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Summary

UK and Ireland classification

EUNIS 2008

JNCC 2015

JNCC 2004

1997 Biotope

EUNIS 2008 -

JNCC 2015 -

JNCC 2004 -

1997 Biotope -

Description

Sheltered, tide-swept, rock with dense Saccharina latissima forest and an under-storey (sometimes sparse) of foliose seaweeds such as Plocamium cartilagineum, Brongniartella byssoides, Ceramium nodulosum, Lomentaria clavellosa and Cryptopleura ramosa. On the rock surface, a rich fauna comprising sponges (particularly Halichondria panicea) anemones (such as Urticina felina), colonial ascidians (Botryllus schlosseri) and the bryozoan Alcyonidium diaphanum. Areas that are scoured by sand or shell gravel may have a less rich fauna beneath the kelp, with the rock surface characterized by encrusting coralline algae, Balanus crenatus or Spirobranchus triqueter. Good examples of this biotope may have maerl gravel or rhodoliths between cobbles and boulders. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Depth range

-

Additional information

-

Listed By

Further information sources

Habitat review

Ecology

Ecological and functional relationships

Tide-swept areas provide favourable locations for rapid growth of a variety of suspension feeding species and therefore competition for space between them. The sponges Halichondria panicea and Hymeniacidon perleve together with other sponge species especially compete for space and may overgrow each other or, more often, grow against each other in a mutual stand-off whilst extensively overgrowing other encrusting fauna especially Balanus crenatus. Animals such as Halichondria panicea and Botryllus schlosseri are likely to predominate over algae in growing on kelp stipes and may engulf the fronds of red algae.
Where massive growths of the sponge Halichondria panicea occur, they may provide a significant habitat for other species especially amphipods and Caprella linearis appears to be chemically attracted to the sponge. The fauna associated with sponges may be a significant food source for fish (Peattie & Hoare, 1981).
Grazing species, especially chitons, do occur and may maintain rocks clear of epibiota except for encrusting coralline algae.

Seasonal and longer term change

No specific information has been found in relation to this biotope. However, red algae are likely to show a seasonal change in condition of the fronds.

Habitat structure and complexity

There are a wide range of microhabitats within this biotope. They include sediments, sometimes maerl, where infauna will occur, underboulder habitats, the sides and tops of boulder which often have different dominant species, the interstices of massive sponge growths, the holdfasts of kelp plants and the fronds of kelps and other algae.

Productivity

No specific information found has been found but the communities in this biotope are likely to be highly productive. The biotope occurs in shallow depths where both high light intensity and, because of tidal flow, high supply of nutrients to algae will result in high primary productivity. Secondary productivity will also be high as the flow of suspended food is high.

Recruitment processes

The characterizing species in this biotope all have planktonic larvae and are fairly short-lived. There is therefore high recruitment and high turnover.

Time for community to reach maturity

The community would probably reach maturity within 3-4 years although recruitment of additional species to the biotope would continue for some further time.

Additional information

This biotope is remarkable because, even in shallow depths where algae normally predominate, animals - especially sponges - are likely to be dominant. It seems that sponges will out-compete algae where food supply is sufficient.

Species composition

Species found especially in this biotope

Rare or scarce species associated with this biotope

Additional information

This MarLIN sensitivity assessment has been superseded by the MarESA approach to sensitivity assessment. MarLIN assessments used an approach that has now been modified to reflect the most recent conservation imperatives and terminology and are due to be updated by 2016/17.

Explanation

The species selected to assess sensitivity in this biotope are predominantly space occupiers that characterize the biotope. Saccharina latissima does and Halichondria panicea may include important structural features supporting other species. Delesseria sanguinea is selected as a representative red algae which, although not listed as characterizing species in the biotope classification, does occur in the biotope and has significant research information that should represent other red algal species. Although encrusting red algae occur in scoured situations in this biotope, they are not included as representative species here as a distinctive feature of this biotope is that overgrowth by animals is extensive.

Some species, especially Saccharina latissima, are likely to protrude above smothering material. Others such as the active suspension feeders and foliose algae are likely to be killed by smothering. For recoverability, see Additional Information.

Increased suspended sediment levels will reduce the amount of light reaching the seabed and may therefore inhibit photosynthesis of the algal component of the biotope. However, the biotope occurs in very shallow depths and algae are likely to survive. Increased suspended sediment is unlikely to have a significant effect in terms of smothering by settlement in the regime of strong water flow typical of this biotope. However, silt may clog respiratory and feeding organs (especially sea squirts). Since many of the species in this biotope live in areas of high silt content (turbid water) it is expected that they would survive increased levels of silt in the water. Both algae and animals would suffer some decrease in viability. On return to lower suspended sediment levels it is expected that recovery of condition will be rapid.

Decreased suspended sediment levels will increase the amount of light reaching the seabed and may therefore increase competitiveness of the algal component of the biotope. Suspended sediment may include organic matter and a decrease may reduce the amount of food available to suspension feeding animals. Both algae and animals would suffer some decrease in viability. On return to higher suspended sediment levels it is expected that recovery of condition will be rapid.

The biotope is predominantly sublittoral but does extend onto the shore and therefore has some ability to resist desiccation. On a sunny day at low water of spring tides, damage (bleaching) is likely to occur to the Saccharina latissima plants but not destroy them completely. Species living below the kelp fronds will be protected by them from the worst effects of desiccation. Sponges, such as Halichondria panicea, are likely to withstand some desiccation as they hold water.

The biotope is predominantly sublittoral and the dominant species (Saccharina latissima) and many of the subordinate species, especially solitary sea squirts, are unlikely to survive an increased emergence regime. Several mobile species are likely to move away. However, providing that suitable substrata are present, the biotope is likely to re-establish further down the shore within a similar emergence regime to that which existed previously.
For recoverability, see additional information below.

Increase in tidal flow rates may dislodge substrata (especially where large plants of Saccharina latissima subject to drag are attached to cobbles). Also, increased water flow rate may result in certain species being unable to feed when water flow is likely to damage feeding organs (see Hiscock 1983). However, it is unlikely that species attached to non-mobile substrata in the biotope will be killed by an increase in flow rate. Therefore a decline in the abundance of some species that are swept away is suggested with some reduction in viability of others depending on whether the current velocity reaches a high enough level to inhibit feeding.

Decreased water flow will lead to a reduced competitive advantage for suspension feeding animals especially sponges which will decline in growth rate so that seaweeds will tend to become more dominant. Reduction in water flow rate will also allow settlement of silt with associated smothering. It is therefore expected that, although there might be only a minor decline in species, the biotope will change, possibly to SIR.Lsac.Cod (Sparse Laminaria saccharina with Codium spp. and sparse red seaweeds on heavily silted very sheltered infralittoral rock). Because the biotope is likely to change, an intolerance of high is given. For recoverability, see Additional Information.

The biotope occurs in warmer and colder parts of Britain and Ireland and similar assemblages of species are known to occur in Scandinavia and in Brittany so that long-term temperature change is unlikely to cause a significant impact. However, exposure to high temperatures for several days may produce stress in some component species but recovery would be expected to be rapid.

The biotope occurs in warmer and colder parts of Britain and Ireland and similar assemblages of species are known to occur in Scandinavia and in Brittany so that long-term temperature change is unlikely to cause a significant impact. There is a single record of Halichondria panicea being adversely affected by frost during the 1963/64 winter (Crisp, 1964).

Several of the characteristic species are algae that rely on light for photosynthesis. Reduction in light penetration as a result of higher turbidity is unlikely to be fatal to algae in the short term but in the long term will result in a reduction in downward extent and therefore overall extent of the biotope. Species richness may decline in the long-term as algae are unable to survive high turbidity and low light but reduced extent of the biotope (depth limits) is the most significant likely decline.

This is a fundamentally sheltered coast biotope with species that do not appear to occur in wave exposed situations. Increased wave action is likely to dislodge Saccharina latissima plants and interfere with feeding in solitary tunicates. Massive growths of Halichondria panicea are likely to be displaced. Although 'major decline' is indicated with regard to species richness, the results of increased wave exposure would be replacement of biotope-characteristic species with others and the development of a different biotope. A change of biotope means high intolerance. On return to previous conditions, the 'new' biotope would have to degrade before SIR.Lsac.T developed. Nevertheless, such a change should occur within five years and a recoverability of high is indicated (see additional information below). For recoverability, see Additional Information.

Saccharina latissima, other algae, sponges and the large solitary tunicates are likely to be removed from the substratum by physical disturbance. Physical disturbance will also overturn boulders and cobbles so that the epibiota becomes buried. Mortality of species is therefore likely to be high although many, particularly mobile species, will survive. For recoverability, see additional information.

Although many of the species in the biotope are sessile and would therefore be killed if removed from their substratum, displacement will often be of the boulders or cobbles on which the community occurs in which case survival will be high. The 'Intermediate' ranking given here supposes that some individual sessile organisms will be removed and die. Mobile organisms such as the prosobranchs in the biotope are likely to survive displacement. Recovery rate assumes that the characteristic species of the biotope will remain, albeit in lower numbers. However, where species have been removed, most have a planktonic larva and/or are mobile and so can migrate into the affected area. For recoverability, see Additional Information.

Chemical Pressures

Several of the species characteristic of the biotope are reported as having high intolerance to synthetic chemicals. For instance, Cole et al. (1999) suggested that herbicides such as Simazine and Atrazine were very toxic to macrophytic algae. Hiscock & Hoare (1974) noted that almost all red algal species and many animal species were absent from Amlwch Bay in North Wales adjacent to an acidified halogenated effluent. Red algae have also been found to be sensitive to oil spill dispersants (O'Brien & Dixon 1976; Grundy quoted in Holt et al., 1995). Recovery is likely to occur fairly rapidly. For recoverability, see Additional Information.

Heavy metal contamination

No information

Not relevant

No information

Insufficientinformation

Not relevant

Insufficientinformation.

Hydrocarbon contamination

Intermediate

High

Low

Decline

Low

Red algae have been found to be sensitive to oil and oil spill dispersants (O'Brien & Dixon, 1976; Grundy quoted in Holt et al., 1995). Foliose red algae in the biotope may therefore be subject to bleaching and death. Holt et al. (1995) reported that Saccharina latissima (studied as Laminaria saccharina) had been observed to show no discernible effects from oil spills. The shallow nature of this biotope suggests that oil might diffuse in significant quantities to the biota. However, the presence of strong tidal flow makes it likely that oil will be flushed away. Overall, an intolerance of intermediate is suggested.

Radionuclide contamination

No information

Not relevant

No information

Insufficientinformation

Not relevant

Insufficientinformation.

Changes in nutrient levels

Low

High

Low

Minor decline

Low

Evidence is equivocal. For Saccharina latissima (studied as Laminaria saccharina), Conolly & Drew (1985) found that plants at the most eutrophic site in a study on the east coast of Scotland where nutrient levels were 25% higher than average exhibited a higher growth rate. However, Read et al. (1983) reported that, after removal of a major sewage pollution in the Firth of Forth, Saccharina latissima (studied as Laminaria saccharina) became abundant where previously it had been absent. Increased nutrients may increase the abundance of ephemeral algae and result in smothering or changing the character of the biotope. Any recovery is likely to be high as species are unlikely to be completely lost and have planktonic larvae and high growth rates. See also Additional Information.

The biotope occurs in situations that are naturally subject to fluctuating or low salinities: it grows in areas where freshwater run-off dilutes near-surface waters and most components are likely to survive reduced salinity conditions. For instance, Saccharina latissima (studied as Laminaria saccharina) can survive in salinities of 8 psu although growth is retarded below 16 psu (Kain, 1979). Delesseria sanguinea is also tolerant of salinities as low as 11 psu in the North Sea whilst Halichondria panicea occurs in the reduced salinity of the western Baltic probably as low as 14 psu. Most characteristic species are likely to survive reduced salinity but species that are lost are likely to have planktonic larvae and recolonize rapidly. See also Additional Information.

The biotope occurs in areas where still water conditions do not occur and so some species may be intolerant of hypoxia. Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. However, on return to oxygenated conditions, rapid recovery is likely.

Biological Pressures

There is little information on microbial pathogen effects on the characterizing species in this biotope. However, Saccharina latissima may be infected by the microscopic brown alga Streblonema aecidioides. Infected algae show symptoms of Streblonema disease, i.e. alterations of the blade and stipe ranging from dark spots to heavy deformations and completely crippled thalli (Peters & Scaffelke, 1996). Infection can reduce growth rates of host algae. It is likely that microbial pathogens will have only a minor possible impact on this biotope.

The non-native species currently (October 2000) most likely to colonize this biotope is Sargassum muticum which is generally considered to be a 'gap-filler'. However, it may displace some native species. Potential non-native colonists are the kelp Undaria pinnatifida which may significantly displace Saccharina latissima but not change other components.

Extraction of Saccharina latissima may occur but the plant rapidly colonizes cleared areas of the substratum: Kain (1975) recorded that Saccharina latissima (studied as Laminaria saccharina) was abundant six months after the substratum was cleared so recovery should be rapid. Associated species are unlikely to be affected by removal of Saccharina latissima unless protection from desiccation on the lower shore is important.

Additional information

RecoverabilityThe main characterizing species, Saccharina latissima, rapidly colonizes cleared areas of the substratum and Kain (1975) recorded that Saccharina latissima (studied as Laminaria saccharina) was abundant six months after the substratum was cleared so recovery should be rapid. The main species covering rock, Lithophyllum incrustans, grows at a rate of only <7 mm a year (Irvine & Chamberlain, 1994) and will take much longer to colonize. Most other characterizing species have a planktonic larva and/or are mobile and so can migrate into the affected area. Many or most of the species in the biotope grow rapidly (for instance, Halichondria panicea increases in size by about 5% per week (Barthel, 1988). However, coralline encrusting algae and maerl, where present, are likely to recover more slowly as growth rates are low. Although some species might not have recovered full abundance within five years, the appearance of the biotope will be much as before the impact. Overall, the community is likely to recolonize rapidly and a recoverability of high is given.

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